A THEORY OF IONOSPHERIC CURRENTS ASSOCIATED WITH AURORAE. II

Abstract

The average ionospheric current flowing along a long homogeneous arc, is calculated numerically on the basis of the theory developed in Part I. This is compared with the auroral current necessary to produce the observed magnetic disturbance at Saskatoon (52.1 °N., 106.6 °W.) and Flin Flon (54.7 °N., 102.0 °W.) for an arc which satisfies the conditions required by the theory. A good order of magnitude agreement between the two values is obtained.The theory also shows that, in general, the magnitude of the line current is proportional to the intensity of the arc, but that when the ionospheric wind is directed along the arc, the line current vanishes. Thus a simple explanation of the occurrence of arcs with no associated magnetic disturbance is provided.A relationship between the average magnetic disturbance due to arcs and the ionospheric wind velocity is also established. The hourly variation of magnetic disturbance during aurorally active hours at Saskatoon and Flin Flon is shown to predict ionospheric wind velocity variations which agree well with those obtained by radio measurements.